1. Field of the Invention
The present invention generally relates to devices and processes for pre-formatting optical media such as optical tape, and more particularly to a process of producing or fabricating an embosser drum for use in performing continuous roll-to-roll nanoimprint lithography to pre-format optical tape.
2. Relevant Background
Optical tape is a type of digital storage media that is generally in the form of a long and narrow strip of plastic that is designed to wind around a number of reels and be moved in first and second opposite longitudinal directions by a drive motor (the reels and drive motor being known as a “tape transport system”). As the optical tape is moved about the reels by the drive motor, digital content (e.g., binary data in the form of a series of encoding patterns) may be written and read by one or more lasers which may be embodied in one or more optical pickup units (OPUs).
The encoded binary data may be in the form of “pits” (e.g., indentations, indicia) and “lands” (e.g., the portion of the tape between adjacent pits) disposed on one or more encoding or recording layers (e.g., each including a dye recording layer, a phase change material such as AgInSbTe, and/or a semi transparent metal reflecting layer). Pits result in decreased (e.g., distorted) reflection when read by a laser and may equate to a binary value or zero or “off” whereas lands reflect laser light and may equate to a binary value of one or “on”. Generally, the smaller the indicia are on the optical media, the higher the capacity is of the optical media.
To enhance positioning, tracking, focusing, and the like in relation to the optical tape and related componentry (e.g., OPUs, hardware, control system, and/or the like), one or more physical features may be incorporated into one or more surfaces of the optical tape at the time of manufacture (i.e., the optical tape may be “pre-formatted”). For instance, nanometer scale patterns may be imprinted in the optical tape by way of mechanically deforming the tape (e.g., one or more monomer or polymer layers of the tape) and curing the tape with heat or UV light during the imprinting. One type of nanometer scale pattern may be a series of grooves defined on the surface of the optical tape. Encoded data in the form of pits and the resultant lands between adjacent pits may be formed within grooves and/or on the portion of the optical surface between adjacent grooves (which may also be referred to as “lands”). The encoding may utilize any appropriate recording process such as helical scan recording, quadruplex recording, and/or the like. In any event, forming the encoded pattern of pits and lands within and/or in relation to the grooves facilitates tracking of data by OPUs. In some arrangements, the pre-formatting may include forming “wobbled” grooves in the optical tape where the wobbled features on the edges of each groove provide addressing information in relation to the data tracks.
In relation to the pre-formatting of optical tape, “Roll-to-Roll Nanoimprint Lithography” has been proposed as a method to pre-format optical tape media with nanostructure imprints such as a series or set of generally parallel wobbled grooves. This process generally involves transporting the optical tape through a number of operational stages by way of a tape transport system (e.g., system of reels, tensions sensors, and the like). Among others, operational stages typically include coating and sputtering, embossing and curing. In relation to the embossing stage, the optical tape is typically wound around what may be referred to as an “embossing” or “embosser” drum (e.g., roller) that includes a pattern of nanostructures which serves to emboss the pattern into the surface of the optical tape.